A stereo echo canceler with pre-processing for correct echo-path identification

A new stereo echo canceler with pre-processing for correct echo-path identification is proposed. The pre-processing is accomplished by a two-tap time-varying filter which delays the input signal periodically by one sample in one of the two channels. Aliasing components and audible clicks by pre-processing are made inaudible by selecting appropriate parameters for the filter. Simulations with the NLMS algorithm and a white Gaussian signal confirm the correct echo-path identification. For speech signals, the convergence speed of the proposed echo canceler is more than three times faster than that of an echo canceler with nonlinear transformations. Results of a subjective listening test demonstrate that quality of the pre-processed signals is 4.38 using the CCIR five-grade impairment scale. This is acceptable for general teleconference applications.